Applications exist for dispensing medications by way of inhaler devices. Such devices long have been popular for use by persons with asthma to deliver vapor medications stored under pressure, through a chamber, and ultimately, to an inhaler which is placed in the mouth of the person requiring the medication. The medicine which is dispersed in asthma inhalers, however, is vaporized liquid, which is placed in a pressure dispenser associated with the inhaler. Whenever a dosage of medicine is to be delivered, a valve is momentarily opened to dispense and vaporize the stored liquid for inhalation by the user.
In recent years, experimentation has been undertaken for delivering powdered medicine by way of an inhaler. Particularly promising is the development of insulin powder which may be inhaled, thereby eliminating the need for injected insulin and all of the problems which are attendant with medications which must be injected at frequent intervals. For delivering powdered medication such as insulin powder, the inhaler device must be designed to blow a stream of compressed air through the powder, creating a cloud of tiny medication particles which then may be inhaled from the device.
The Haber U.S. Pat. No. 5,287,850 is directed to a powdered pharmaceutical inhaler mechanism. The device of this patent delivers pressurized air through a coiled tube for dispersing and driving powdered pharmaceutical into the mouthpiece for inhalation by the user. Different parts of the mechanism shown in this patent are designed to be moved from a loading position to a delivery position; and this includes the coiled tube which interconnects these parts. The movement of the tube in this device, however, is quite limited, as is readily apparent from an examination of the device shown in the patent.
For inhaler mechanisms where there is a manual pressurization of a charge of air, different parts of the mechanism need to be moved toward and away from one another a greater distance than the parts of the Haber patent. Typically, such mechanisms require movement of from one-half inch to 1xc2xd inches in order to effect the desired charging and cocking of the mechanism. In such manual pressurization mechanisms, it is necessary to utilize a flexible tube to interconnect the charged air with the delivery portion. This tube must be capable of handling the air pressure charge, as well as extension and retraction as the device is utilized. Because there is a relatively long distance of travel between the parts in the various stages of operation, it has been found that a sufficiently long straight length of plastic tubing tends to bend and rub against other internal parts. This rubbing ultimately causes weakness in the wall of the tube, resulting in failure of the device. Because of the relatively large distance of travel in such a manual charging and cocking mechanism, it also is possible to crimp or kink the tube, which also leads to incomplete or ineffective delivery of the medication, and a failure of operation of the device.
It is desirable to provide a machine and method for forming a thermoplastic tube, with a uniform cross-sectional thickness throughout its length, as a helical spring, which can be extended and released to its thermoset, coiled, biased condition repeatedly for use in manually charged powdered medication delivery systems.
It is an object of this invention to provide a method for forming a helical coil in a length of hollow cylindrical plastic tubing.
It is another object of this invention to provide a method for forming a helical coil in a length of hollow cylindrical plastic tubing, where the wall thickness of the tubing is uniform throughout its length, including the helical coil.
It is an additional object of this invention to provide a machine for forming a helical spring coil in a length of hollow cylindrical thermoplastic tubing.
It is a further object of this invention to provide a method and machine for forming a thermoset spring coil in a length of hollow cylindrical thermoplastic tubing.
In accordance with a preferred embodiment of this invention, a method and machine form a helical coil in a length of hollow cylindrical thermoplastic tubing. This is accomplished by clamping the ends of a predetermined length of plastic tubing between first and second opposed spaced clamping mechanisms, which may be in the form of first and second sections of a mandrel. The clamping mechanisms, or first and second mandrel sections, then are rotated relative to one another and simultaneously moved toward one another to form a helical coil in the tubing. Where first and second mandrel sections are employed, the helical coil is formed around the mandrels as they move toward one another. Once the coil is formed, the region of at least the coil portion of the tubing is heated to the thermosetting temperature of the tubing to heat-form the coil in the tubing. Following the heating to set the coil, the coil and tubing are cooled; and the spring coil tube is released from the machine.